1. Field of the Invention
The invention relates to the field of hoists and, more particularly, to a portable hoist system for mounting to rails.
2. Background of the Related Art
Safety and rescue workers such as fireman are commonly confronted with situations where it is necessary to raise or lower persons and objects between different elevations, such as between the ground level and an upper level of tall structures such as buildings and bridges. During rescue operations, it is frequently impossible to access tall structures using a conventional vehicle-mounted ladder or elevated platform due to time, space or safety concerns.
Portable lifting devices are known for use on the roofs of buildings to lift or lower objects. For example, U.S. Pat. No. 5,341,898 to Baziuk and U.S. Pat. No. 2,569,821 to Maxeiner disclose portable lifting devices which are foldable or collapsible, and constructed to be supported by a roof surface without fixed attachment.
U.S. Pat. No. 4,270,628 to Anderson discloses an elevator device comprised of a trolley permanently attached to a pair of rails which are detachably secured to upstanding supports provided on roofs of buildings.
The above-described lifting devices for use on roofs of buildings are not suitable for portable use on fixed rails and, especially, on an elevated railroad bridge extending over land or water. Maintenance work and rescue operations performed on such railroad bridges involve added difficulties. While it is possible to store lifting devices on or near to roofs to have them available at all times, the same is not possible with respect to railroad bridges. Furthermore, bridges located at remote locations and lacking nearby access roads further increase the difficulty of providing lifting devices in emergencies.
Thus, in view of the above-described disadvantages associated with the known devices, there has been a need for a lifting and lowering device for objects, materials and persons which is portable, easily assembled for use and disassembled for storage or transport, and suitable for use on rails.